This invention relates to a pressure control valve assembly for automotive fluid brake systems to prevent the skidding or slipping of the rear wheels.
In order to obviate the skidding of the rear wheels of a motor vehicle, fluid brake systems have been provided with a pressure control valve assembly to reduce the ratio of rear wheel brake pressure to front wheel brake pressure during rapid deceleration. The control valve assembly comprises a differential piston slidably received in a stepped bore formed in a housing and valve means mounted in the piston. The valve means is selectively opened and closed in accordance with the movement of the piston to effect the above brake pressure control.
In this conventional pressure control valve assembly briefly described above, the piston is constructed to assume a position spaced apart from a wall section of the housing when the fluid pressure on the master cylinder side is higher than a so-called switchover point pressure. When the depression on the brake pedal is released to allow the fluid pressure on the master cylinder side to fall beyond the switchover point pressure, the piston is moved into a position where it abuttingly engages with the housing under the bias of a spring. In this instance, the rapid release of the fluid pressure from the control valve assembly results in the piston rapidly striking against the wall section of the housing, producing an unpleasant sound.